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The origins and build of the African elephant

2 March 2015

The earliest ancestor of all the elephants was the trunkless, pig-like Moeritherium of about 60 cm tall that is known to have lived in the Al Fayum Swamp in Egypt and along the fringes of the Tethys Sea between Africa and Asia. This sea disappeared when the Indian tectonic plate, that broke away from Gondwana in the southern hemisphere, collided with Asia some 50 million years ago to form the Himalaya Mountains. What is the Sahara Desert now was a mosaic of swamps and plains at that time.www.leopard.tv

Five families of the Order Proboscidea (mammals with trunks), which includes the living elephants and numerous extinct forms, later developed as climates and the distribution of the land masses changed, but only the family Elephantidae has survived. It is ironic that the human migration from Africa some 65 to 50 million years ago has led to much of this extinction because they hunted the megafauna as a source of food, while monetary greed among humans are now threatening the existence of the last surviving family of the elephants.

The family Elephantidae includes the modern elephants, two species of mammoth, the imperial mammoth and the woolly mammoth. The woolly mammoth Mammuthus primigenius was adapted to live in cold climates and had a coat of long, dark rust-coloured hair of about 500 mm long, a thick skin over of an extensive layer of fat, small ears, long tusks that curled inwards, swollen foreheads, and backs that sloped more towards their hindquarters than in modern elephants. They survived until after humans had occupied much of the World and are often depicted in early cave paintings. The frozen woolly mammoths that are still being found in the far northern latitudes have allowed the determination of their entire genetic make-up or genome. Their frozen meat was once served by one of the Russian Tsars during a banquet in Leningrad.

The fossil elephant genus Stegodon that lived in Asia until a few million years ago was the ancestor of the living Asian and African elephants. Fossils of the Asian elephant genus Elephas have been found at Swartkrans and Sterkfontein in Gauteng and at Makapan’s Cave in the Limpopo province, however, this genus could once have been the dominant type of elephant in Africa although it no longer occurs there.

Both the Asian and African elephant are intelligent and can be domesticated. The Asian elephant Elephas maximus was the first to be domesticated some 3000 years ago. Domesticated forest elephants Loxodonta cyclotis were used in the Democratic Republic of the Congo in Africa as recently as 1982 to level ground for a landing strip for aircraft. However, the savanna elephant of eastern and southern Africa Loxodonta africana is the most temperamental of the three living types of elephant and is less suitable as a working animal. Relative to the overabundance of food in the Asian forests, the elephants of the African savannas also require more time than the Asian elephants to eat enough food which leaves less time for working effectively with them.www.leopard.tv

Although the African forest and savanna elephant can hybridize where they come into contact, they are genetically and morphologically quite distinct. The ear of an African savanna elephant has three, triangular lobes with the tip of the ear being directed downward, but the ear of the African forest elephant has no well-developed lobe and is much more rounded. While the African savanna elephant has four distinct toes on the forefeet and three on the hind feet the African forest elephant has five toes on the forefeet and four on the hind feet. However, being mammals, both species have five digits on the forefeet and hind feet but some toes have become atavistic while the nails have become lost in the African savanna elephant, possibly because of the nature of the savanna terrain.

The best distinguishing characteristic between the African forest and savanna elephant is the shape and articulation joint of the lower jaw. The lower jaw of a forest elephant forms a long, narrow spout with ovoid articulation joints as opposed to the short and wide lower jaw with spherical articulation joints in the savanna elephant. Provisional genetic research has indicated that there may possibly be a third species of African elephant which has been derived from an ancient gene pool before the development of the forest and savanna elephants, but no conclusive evidence for this exists yet.

 

The African savanna elephant

As little is known about the African forest elephant, the African savanna elephant will consequently be discussed further. It is the largest land mammal in terms of shoulder height, with the desert-dwelling Fenykovi’s elephant ecotype from north-western Namibia that is mounted in the National Museum in Washington, DC in the USA being the largest known specimen, with a shoulder height of just more than 4 m as opposed to up to 3,45 m in the rest of Africa. The weight of an adult bull varies from 5000 to some 6500 kg. The bulls grow continually but the cows reach their maximum growth when they are 35 to 40 years old. The skin colour is grey to brownish-grey. The trunk contains a multitude of muscles and has a prehensile tip on the upper and lower edge. The small eyes are green or hazel in colour and do not have tear ducts. The ear flaps may be as large as 2 m vertically and 1,2 m horizontally and the vascular system on the back of the ears serve for temperature regulation. The water loss from the skin for evaporative cooling of an elephant weighing only 1200 kg has been measured at 30 litres per day.

As members of; the Testiconda, the testes remain in the body cavity. The two teats are between the forelegs. There is no pleural cavity and the sexes can be differentiated in the field by the profile of the forehead which is angular in a cow and rounded in a bull. After reaching an age of 15 years, the width of the lower jaw is also different between the sexes. Temporal glands on both sides of the head increasingly secrete a fluid as stress increases. In males this often occurs during musth when they become sexually active and aggressive.www.leopard.tv

Because of weight distribution caused by carrying the massive head and tusks, the forefeet are larger and more rounded than the hind feet. The soles of the feet are horny and cracked superficially in patterns which are distinct for various individuals. Reliable aging can only be done by using the replacement status of the six molar teeth in each jaw. This replacement ceases at an age of some 47 years. When the wear of the last molars is complete, an elephant in the wild will no longer be able to feed well and will eventually die of starvation. The mean lifespan of an elephant is some 60 years. The tusks grow throughout life and are enlarged upper incisors. The heaviest pair of tusks on record that came from Mount Kilimanjaro in Tanzania weighed 102,7 and 97,0 kg respectively, but both were 3,1 m long. Another tusk from Kenia was 3,3 m long. The heaviest pair on record from the Kruger National Park weighed 73,5 and 69,0 kg and came from near Skukuza. Both sexes can also be tuskless. Each molar that is replaced is longer and wider than the previous one.

Since the 17th century, ivory has been a valued global commodity which have since almost threatened the African elephant with extinction. In combination with the rinderpest epidemic the hunting of elephants once almost destroyed the Serengeti grass plains of East Africa because these elephants and fire prevented bush encroachment of these plains. Many elephant populations are still being threatened by human greed for their ivory. From 1700 to 1800 elephant ivory was the basis of the economy of Mozambique, but even in 1544 great quantities of ivory was exported from Delagoa Bay (Maputo) in South Africa. The peak ivory export from South Africa to Europe occurred from 1879 to 1883, most of the ivory originating from the northern parts of southern Africa. Only remnant populations have remained in South Africa, with the largest populations in the Kruger and Addo Elephant National Parks.

 

Reference:

Skinner, J D & C T Chimimba (Eds) 2005. The mammals of the southern African subregion, third edition. Cambridge: Cambridge University Press, pp 51 - 55.

 

article by Prof J du P Bothma

 

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